Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtp (Exim 4.72) (envelope-from ) id 1Tiawt-0005e4-EI for pgsql-performance@arkaria.postgresql.org; Wed, 12 Dec 2012 01:17:24 +0000 Received: from localhost ([127.0.0.1] helo=postgresql.org) by malur.postgresql.org with smtp (Exim 4.72) (envelope-from ) id 1Tiaws-0002ex-EX for pgsql-performance@arkaria.postgresql.org; Wed, 12 Dec 2012 01:17:22 +0000 Received: from magus.postgresql.org ([2a02:c0:301:0:ffff::29]) by malur.postgresql.org with esmtp (Exim 4.72) (envelope-from ) id 1Tiawr-0002eB-9I for pgsql-performance@postgresql.org; Wed, 12 Dec 2012 01:17:21 +0000 Received: from mail-la0-f43.google.com ([209.85.215.43]) by magus.postgresql.org with esmtp (Exim 4.72) (envelope-from ) id 1Tiawo-0003HZ-8T for pgsql-performance@postgresql.org; Wed, 12 Dec 2012 01:17:20 +0000 Received: by mail-la0-f43.google.com with SMTP id z14so92181lag.2 for ; Tue, 11 Dec 2012 17:17:17 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=content-type:mime-version:subject:from:in-reply-to:date:cc :message-id:references:to:x-mailer; bh=51gp9zTWE3ljX1e7iw/R+uyh4UK4lqxGu9+718PykIw=; b=I7EleGzSQCaJJPa7aZBpIK1qUrev2P6KyMsRqnMp+heQ2eGXyklWHNLJYoaE9NDn0/ bnaD0RONv90/544S0zvNl656Lp/c3bYTdPM5fnqGK6z375i2GYF9s4sg7AONMoE7iAi/ qTgJ95putAaLMW/e4yNRYBoDjMgaKkqJaSs2PHSV468NnuUuP5XEoalCiEeVaGxWE9Bz +l/tQU2xTAuzCRpDyMwsmgbVhFfE9be4wgF7wM8YmNcrUIiEyLduqGlPTUm0Qa1wy8WO N0E6xrpT3J9qqOm01k8fMqBUc4sPVur6At6B2fRpTUPmfuUSM0LzQuIiDLoHn26Isrpv ZMwQ== Received: by 10.152.111.161 with SMTP id ij1mr34423lab.28.1355275037334; Tue, 11 Dec 2012 17:17:17 -0800 (PST) Received: from [192.168.20.5] ([176.195.39.85]) by mx.google.com with ESMTPS id sj3sm9944682lab.2.2012.12.11.17.17.15 (version=TLSv1/SSLv3 cipher=OTHER); Tue, 11 Dec 2012 17:17:16 -0800 (PST) Content-Type: multipart/alternative; boundary="Apple-Mail=_58D1A5D2-568D-470C-A160-860223BCA682" Mime-Version: 1.0 (Mac OS X Mail 6.2 \(1499\)) Subject: Re: Do I have a hardware or a software problem? From: Evgeny Shishkin In-Reply-To: <50C7D7D2.4070605@2ndQuadrant.com> Date: Wed, 12 Dec 2012 05:17:14 +0400 Cc: =?iso-8859-1?Q?Niels_Kristian_Schj=F8dt?= , Jeff Janes , "pgsql-performance@postgresql.org" Message-Id: <2BCB6843-1396-42C9-A5BF-21C7C978FF4B@gmail.com> References: <8F7661E7-D6D4-4334-8C6A-A8B6C56A2C3F@autouncle.com> <50C7351C.30407@2ndQuadrant.com> <4507A68A-3CD5-4283-AFA5-1C0593427E14@autouncle.com> <67FBF3AF-5C6A-45D4-9206-7257C8C01C5E@gmail.com> <50C7D7D2.4070605@2ndQuadrant.com> To: Craig Ringer X-Mailer: Apple Mail (2.1499) X-Pg-Spam-Score: -2.7 (--) List-Archive: List-Help: List-ID: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: X-Mailing-List: pgsql-performance Precedence: bulk Sender: pgsql-performance-owner@postgresql.org --Apple-Mail=_58D1A5D2-568D-470C-A160-860223BCA682 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=windows-1252 On Dec 12, 2012, at 5:03 AM, Craig Ringer wrote: > On 12/12/2012 06:44 AM, Evgeny Shishkin wrote: >>=20 >> On Dec 12, 2012, at 2:41 AM, Niels Kristian Schj=F8dt = wrote: >>=20 >>> Are you using a hardware based raid controller with them? >>>=20 >> Yes, of course. Hardware raid with cache and bbu is a must. You can't = get fast fsync without it. >=20 > Most SSDs should offer fairly fast fsync without a hardware RAID = controller, as they do write-back caching. The trick is to find ones = that do write-back caching safely, so you don't get severe data = corruption on power-loss.=20 >=20 Actually most of low-end SSDs don't do write caching, they do not have = enough ram for that. Sandforce for example. > A HW RAID controller is an absolute must for rotating magnetic media, = though. >=20 >> Also mdadm is a pain in the ass and is suitable only on amazon and = other cloud shit. >=20 > I've personally been pretty happy with mdadm. I find the array = portability it offers very useful, so I don't need to buy a second RAID = controller just in case my main controller dies and I need a compatible = one to get the array running again. If you don't need a BBU for safe = write-back caching then mdadm has advantages over hardware RAID. >=20 If we are talking about dedicated machine for database with ssd drives, = why would anybody don't by hardware raid for about 500-700$? =20 > I'll certainly use mdadm over onboard fakeraid solutions or low-end = hardware RAID controllers. I suspect a mid- to high end HW RAID unit = will generally win. >=20 > --=20 > Craig Ringer http://www.2ndQuadrant.com/ > PostgreSQL Development, 24x7 Support, Training & Services --Apple-Mail=_58D1A5D2-568D-470C-A160-860223BCA682 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=windows-1252 craig@2ndQuadrant.com> = wrote:
=20 =20 





--=20
 Craig Ringer                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services

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